What are the critical parameters to monitor during slurry preparation for Slurry TBM operation?

During slurry preparation for Slurry TBM operation, several parameters are critical to monitor to ensure the slurry has the desired properties for face support and efficient transport of excavated material. Slurry density is important because it directly affects the slurry's ability to balance earth and water pressures at the tunnel face. Density is typically controlled by adjusting the concentration of solids in the slurry. Viscosity influences the slurry's flow behavior and its ability to form a stable filter cake on the excavation face. Viscosity is affected by the type and concentration of clay or polymers in the slurry. pH levels influence the stability and reactivity of the slurry. Maintaining the correct pH helps prevent corrosion of the TBM components and ensures that the slurry does not react negatively with the surrounding soil or rock. Sand content is an important parameter. Excessive sand content can increase wear on the TBM and reduce the slurry's ability to form a filter cake. Controlling the sand content involves using screens or hydrocyclones to remove sand from the slurry. Polymer or bentonite concentration dictates the slurry's performance. Proper concentrations are essential for achieving the desired viscosity, density, and filtration properties. Filtration properties must be monitored. These include the filter cake's thickness, permeability, and stability. A stable filter cake is essential for preventing groundwater inflow and maintaining face stability. The term 'slurry' refers to a mixture of water and solids, typically bentonite clay or polymers, used to support the tunnel face in a Slurry TBM. 'Slurry TBM' is a type of tunnel boring machine that uses a slurry to support the excavation face. 'Filter cake' is a layer of slurry solids that forms on the excavation face, reducing permeability and providing support.